my 4s battery draining quick lately

hi folks,
lately i have notice my battery life draining down slightly a bit quicker than what i'm used to. i barely make calls very often throughout the day and the phone spend most of it time on standby, but very often i press the power button to check the time and press the power button again to turn off the screen. but not thing unusual from my day to day usage pattern at all.
is there some kind of newer firmware revision that automatically updated over the air that causes this?

i don't normally think about my battery life, but lately the battery cycle pattern change a bit to get my attention to it.

Anyway, I can go about a day and a half to two full days before reaching for the charger. I always have the wifi on, but no Siri or Bluetooth. Data and 3G is always on. I barely talk and barely text. But occational light web browsing while on the go and a lot of emails. Now I barely do Any of that stuff and I got about 60% by half the day.

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